Many complex electronic equipments are constructed of a number of discrete circuit modules in the form of printed circuit boards having circuit paths formed on each side to which may be connected various electrical components. Interconnection of a number of individual circuit boards to form the final equipment is attained by use of connectors having terminals which engage contact pads or circuit termination points formed along one or more of the edges of each circuit board. These circuit board connectors are usually provided with sockets to allow assembly onto arrays of terminal pins mounted in a common plane known as a back plane. The terminal pins are selectively wired and interconnected to complete the particular equipment. The edge connector may also be engaged by a number of individual plug connectors secured to ends of wires of a cable harness.
In many instances, it is necessary that the terminals projecting from an edge connector be soldered to insure good electrical contact between the terminals and the engaged pads on the edge of the circuit board. In the past, a number of soldering expedients have been developed and utilized to solder these edge connectors to the circuit boards. One expedient that is extensively used, contemplates, that prior to assembly of the connector on the board, pre-solder coatings are applied to the contact pads and terminals and then heat is applied to reflow the solder to bond the terminals to the pads.
In another recent expedient, connectors are assembled on the circuit boards with the terminals mechanically pressed against the circuit pads. The boards are loaded into fixtures which are advanced in a vertical loop to pass through a solder application station. Each fixture is provided with a linear cam that is contoured to control closures of switches which in turn control the operation of the component mechanisms comprising the soldering machine. As the fixture approaches the soldering station, facilities are initiated to control the movement of a pair of solder applicators toward the board whereafter solder wires with rosin cores are advanced by a pair of selectively driven wheels to lay the wires onto top surfaces of the advancing terminals. Hot air is directed at the site where the solder wires are laid on the terminals so that the solder wires and the areas immediately adjacent to the soldering site are heated to such an extent that the solder melts, flows into and bonds the junctures of the connector terminals and the contact pads.